The invention relates to a method of producing a composite material and more specifically a process for incorporating z-axis fiber reinforcement into x-y axis composite material.
Traditional composite materials are made up of resin matrix material and a quantity of 2-dimensional fibers, continuous in the x-y axis directions, but laminated in layers to produce a material thickness. Composite material construction, wherein a fiber material such as glass fiber, carbon fiber, or aramid fiber is combined with a matrix material, such as thermoplastic or thermoset resins, is an example of a traditional 2-dimensional structure. The resulting structure is produced from xe2x80x9clayeringxe2x80x9d of the 2-dimensional material (known as plies). Because the matrix is weaker in strength than the fiber (in may cases by at least an order of magnitude), the failure mechanism of these composites when test loaded toward their ultimate strength is a cracking or buckling or separation of the matrix material. When this occurs, the composite is known to have delaminated, or the layers of fiber material have separated.
Attempts have been made to lace or tie multiple layers of 2-dimensional composite materials together with z-axis directional fibers which tie all of the layers together. By doing this, delamination can be delayed or eliminated. Some techniques that have been used include 3-D braiding, 3-D weaving, and z-axis pinning. All of these methods have deficiencies, drawbacks and are expensive and labor intensive.
The Fusco et al U.S. Pat. No. 5,589,015 is directed to a method and system for inserting reinforcing pins in composite structure. Ultra sound energy is applied to the pins and pressure is applied simultaneously to insert the pins into the composite structure to join two laminates or reinforce a single composite structure.
The Childress U.S. Pat. No. 5,935,680 is directed to an interlaced z-axis pin sandwich structure that utilizes a plurality of z-axis pins that extend through the core and into each of the face sheets. The pins are arranged in an interlaced configuration off-normal to provide crack resistance around fasteners for connecting the composite structure to other structural elements in aerospace applications.
The Boyce et al U.S. Pat. No. 4,808,461 discloses a translaminar reinforcement structure that utilizes z-axis reinforcing elements and the method for driving these reinforcing elements into the composite structure as it is subjected to an elevated temperature and decomposes.
The Campbell et al U.S. Pat. No. 5,789,061 discloses a stiffener reinforced assembly and its method of manufacturing. The Boyce et al U.S. Pat. No. 5,667,859 also discloses the use of joining composite parts by including reinforcing elements that pass through the thickness of two composite adherents to be joined. The Campbell et al U.S. Pat. No. 5,827,383 also discloses a stiffener reinforcement assembly and its method of manufacturing.
Other patents that teach the use of tow members that are encapsulated within the foam core and which extend between the opposing face sheets to form a combined composite structure are the Boyce et al U.S. Pat. No. 5,624,622 and the Boyce et al U.S. Pat. No. 5,741,574. The Boyce et al U.S. Pat. No. 5,186,776 teaches a technique for translaminar reinforcement and the method includes heating and softening the composite laminates by ultrasonic energy and then inserting reinforcing fibers therein.
It is an object of the invention to provide a novel method of inserting an unstable reinforcing fiber into a composite laminate for z-axis reinforcement.
It is also an object of the invention to provide novel machinery for inserting an unstable z-axis reinforcing fiber into a composite laminate.
It is another object of the invention to provide a new type of composite material with substantial z-axis fiber reinforcement.
It is a further object of the invention to provide a novel method for producing layer quantities of 3-D bar stock, sheet and composite sandwich structure in a continuous, automated fashion.
The method of inserting an unstable reinforcing fiber into a composite laminate for z-axis reinforcement of the laminate requires a z-axis fiber deposition material. The side plates of the chamber formed between top and bottom plates into which is fed x-y axis material. The side plates of the chamber restrict the edges of x-y axis material. There would be multiple laterally spaced z-axis fiber deposition machines so that multiple z-axis fibers could be deposited into the x-y axis material at the same time. Each would have its own respective aperture in the top plate and the bottom plate and these would be aligned. Below each aperture in the bottom plate is an elongated solid rod having a tapered front tip. This rod is known as the xe2x80x9cpathway deposition Probexe2x80x9d (PDP). The PDP is rotated by a motor and then actuated upwardly through the aperture in the bottom plate, the x-y axis material and the aperture in the top plate. Mounted above each aperture in the top plate is a movable hollow tube whose initial position has its bottom end slightly inserted into the aperture in the top plate. Z-axis fiber bundles are contained on stationary rolls and are free to be drawn from the rolls continuously. The front end of each z-axis fiber bundle is threaded downwardly through one of the movable hollow tubes to a position adjacent its bottom end. There would be structure to resupply a predetermined length of z-axis fiber bundle to each movable hollow tube as a new length is needed.
After the PDP has been actuated upwardly to its upper most position, it is then retracted downwardly to its initial position and simultaneously, the movable hollow tube would travel downwardly through the hole created in the x-y axis material. While this is happening, the tip of the PDP would remain inserted into the bottom end of the movable hollow tube to insure a smooth entry of the hollow tube through the aperture in the x-y axis material created by the PDP. Each z-axis fiber deposition unit has a mechanism for preventing withdraw of z-axis fiber from the x-y axis material when the movable hollow tube is withdrawn upwardly. Once the movable hollow tube has been raised to its upper position, the top end of z-axis fiber that has been inserted into the x-axis material is severed. This would complete a whole cycle. Simultaneously, across the width of the housing each of the other z-axis fiber deposition units would have completed their cycle. The next x-y axis material is stepped forwardly to provide a new position for the z-axis fibers to be deposited. Alternatively, the method could provide structure for stepping the housing rearwardly instead of stepping forwardly the x-y axis composite material.
After the x-y axis material has had the z-axis fibers deposited therein, it travels forwardly to a pultrusion die. Here the heated die cures the composite material of the plies and it exits the dies as a cured 3-D fiber composite material. The material is pulled from the die continuously by the alternate gripping edges of multiple grippers that are attached to motion control hydraulic cylinders.